What is the recommended analgesia regimen for post-total knee replacement (TKR) pain management?

Post-TKR Analgesia Regimen

The optimal analgesia regimen for post-total knee replacement combines an adductor canal block (or femoral nerve block) with multimodal systemic analgesia including scheduled paracetamol, NSAIDs/COX-2 inhibitors, and IV opioids for breakthrough pain. 1

Primary Regional Anesthesia Strategy

Adductor canal block is the preferred regional technique for post-TKR analgesia, with strong evidence demonstrating reduced pain scores and decreased supplemental analgesic requirements 1. The evidence supports:

• Continuous adductor canal catheter technique over single-shot injection for extended analgesia 1
• Femoral nerve block as an equally effective alternative, with Grade A recommendation based on procedure-specific evidence 2
• Either general anesthesia combined with the block, or spinal anesthesia with intrathecal morphine 0.1 mg as alternative primary techniques 1

Critical timing consideration: Initiate the block before surgery ends to ensure adequate analgesic effect in the immediate postoperative period 2

Multimodal Systemic Analgesia Protocol

Baseline Non-Opioid Analgesics (Scheduled, Not PRN)

• Paracetamol (acetaminophen): Administer on a scheduled basis in combination with other analgesics (Grade B recommendation), as it reduces supplemental analgesic use in orthopedic procedures 2, 1
• NSAIDs or COX-2 selective inhibitors: Add unless contraindicated (Grade A for conventional NSAIDs, superior evidence for COX-2 inhibitors) 2, 1
• Single intraoperative dose of IV dexamethasone 8-10 mg for analgesic and anti-emetic effects 1

Opioid Rescue Protocol for Breakthrough Pain

For high-intensity pain:

• IV strong opioids via PCA (Grade A recommendation) combined with non-opioid analgesia 2, 1
• IV PCA is preferred over other administration routes due to improved pain control and higher patient satisfaction (Grade B) 2
• Never use IM administration (Grade B against) due to unfavorable pharmacokinetics, injection pain, and patient dissatisfaction 2

For moderate to low-intensity pain:

• Weak opioids (Grade B recommendation) if non-opioid analgesia is insufficient, always combined with non-opioid analgesics 2, 1
• Weak opioids are not recommended for high-intensity pain (Grade D) 2

Adjunctive Non-Pharmacological Measures

• Cooling and compression techniques (such as Cryo/Cuff) to reduce local inflammation and pain 1

What NOT to Do: Critical Pitfalls

Avoid These Regional Techniques

• Do NOT combine femoral and sciatic nerve blocks: Limited and inconsistent procedure-specific evidence shows no benefit over femoral/adductor canal block alone with systemic analgesia 2, 1
• Do NOT use epidural analgesia: Increased risk of serious adverse events without superior benefits compared to peripheral nerve blocks 2, 1
• Do NOT use lumbar plexus block (posterior approach): Femoral nerve block is equally effective with fewer complications 2

Avoid These Intra-Articular Techniques

• Do NOT use intra-articular local anesthetic and/or morphine: Inconsistent analgesic efficacy in procedure-specific evidence 2
• Do NOT use intra-articular NSAIDs, neostigmine, clonidine, or corticosteroids: Inconsistent transferable evidence 2, 1

Avoid These Neuraxial Adjuvants

• Do NOT use spinal clonidine or spinal neostigmine: Limited evidence and significant side effects 2, 1
• Do NOT use adjuvant peripheral nerve drugs (clonidine, epinephrine): Lack of efficacy in procedure-specific studies 2, 1

Special Considerations

Bilateral TKR

When performing bilateral adductor canal blocks:

• Reduce the total dose of local anesthetic to minimize risk of systemic toxicity 1
• Exercise particular caution in elderly patients or those with significant comorbidities due to increased risk of local anesthetic systemic toxicity 1

Continuous vs Single-Shot Nerve Block

While continuous femoral/adductor canal catheter technique is preferred for extended analgesia 1, the 2008 guideline notes that no firm recommendation could be made between continuous infusion versus single bolus due to heterogeneity in study design at that time 2. However, the more recent 2025 guidance clearly favors continuous catheter technique 1.

Paracetamol Monotherapy

Paracetamol is NOT recommended as a sole agent for high- or moderate-intensity pain (Grade D), but should always be part of combination therapy 2